A detector tube of this type has become known from DE Patent No. 932750. Sticks of a porous sintered material, which are impregnated with the detection reagent, are used as reagent carriers in the prior-art detector tube. The sticks are placed into the tubular glass body of the detector tube such that they are located in the direction of the longitudinal axis of the detector tube. A core, around which the sticks are arranged, is provided within the detector tube to fix the sticks within the detector tube.
The drawback of the prior-art detector tube is that a plurality of sticks impregnated with detection reagent must be introduced into the glass body, and that it is difficult to establish homogeneous flow conditions within the detector tube because of the number of sticks.